Development of an orange juice in-house reference material and its application to guarantee the quality of vitamin C determination in fruits, juices and fruit pulps.

Reference materials are useful for the quality control of analytical procedures and to evaluate the performance of laboratories. There are few and expensive certified reference materials commercially available for vitamin C or ascorbic acid analysis in food matrices. In this study, the preparation and the suitability assessment of an orange juice in-house reference material (RM) for vitamin C analysis in fruits, juices and in fruit pulps is described. This RM was used for the development and full validation of an HPLC method. The results showed excellent linearity (r(2)=0.9995), good accuracy (96.6-97.3%) and precision, as relative standard deviation, ranged from 0.70% to 3.67%. The in-house RM was homogenous and stable at storage conditions (-80°C) during 12 months. According to our results, this in-house RM is an excellent tool to use in quality control and method verification purposes for vitamin C analysis of fruits, juices and fruit pulps matrices. Furthermore, a stabilization solution with perchloric and metaphosphoric acids was developed which prevents degradation of ascorbic acid for a period of 12 months at -80°C.